make space for the dRICh

Make space for the dRICh. This is almost the same as !98 (closed) but with a couple additional changes. These proposed changes bring us closer to consistency with the integration plan. This current MR is to support the current dRICh implementation !72 (merged).

Proposed changes:

• compact/definitions.xml: change ForwardRICH_length from 110 cm to 180 cm, to accommodate the dRICh volume
• compact/definitions.xml: change ForwardTracking_length from 0 cm to 25 cm, which positions the front of the dRICh at 155 cm
• remove compact/gaseous_rich.xml from athena.xml, since we will replace it with the dRICh

Caveat:

• With these changes applied, at first there were some overlaps between EcalEndcapN and cb_DIRC_GVol_Solid_Logic. It seems that one or both of these detectors are not adaptable to changes of ForwardRICH_length and ForwardTracking_length. Recently the DIRC has been commented out in athena.xml, and after rebasing this MR, this overlap issue disappeared. Some details on the overlap are shown below.

compact/definitions.xml

@@ -352,7 +352,7 @@
       ### PID Detector Region Parameters
     </comment>
 
-    <constant name="ForwardRICH_length"       value="1.1*m"/>
+    <constant name="ForwardRICH_length"       value="180.0*cm"/>
     <constant name="ForwardTRD_length"        value="10.0*cm"/>
     <constant name="ForwardTOF_length"        value="3.0*cm"/>
     
@@ -381,7 +381,7 @@
       Generic tracking space allocations
     </comment>
 
-    <constant name="ForwardTracking_length" value="0.0*cm"/>
+    <constant name="ForwardTracking_length" value="25.0*cm"/>
     <comment>This compensates for the asymmetry of the setup</comment>
     <constant name="BackwardTracking_length" value="7.5*cm"/>